The present invention relates generally to devices for implantion into the body in order to connect bone structures and, more specifically, to synthetic ligaments for joining adjacent bone structures such as vertebral bodies in order to promote healing or fusion through relative compression of bone or implant structures.
Certain orthopedic procedures require that adjacent or nearby bone structures be placed in compression against each other to provide support, to promote fusion, or to promote healing generally. While such procedures often rely on the natural tension of surrounding soft tissues, muscles and ligaments, it is sometimes desirable to introduce cable or wire, or other structures, to apply and maintain compression between such bone structures. In instances such as intervertebral fusion, for example, where a disc space is relatively large in the vertical dimension, natural tension is hindered due to ligamentous laxity and, as a result, contact between bone and a fusion device necessary to promote good fusion is diminished.
In various medical procedures wires or cables are used to join or support body structures, such as bone structures or implant structures. Metal or synthetic wires and cables are joined at their ends using surgical knots or connecting devices such as crimping members. Various known cable tensioner devices may be employed to attain desired tensioning in loops formed by tied or crimped wires and cables, and to facilitate safe and efficient procedures.
In certain procedures such as intervertebral repair or fusion, and in instances where an implant may be utilized, it is difficult to efficiently install an effective wire or cable system that safely and precisely maintains a desired positioning and support of the bone or implant structures. This is particularly true when the repair or fusion is effected from the anterior side.
In other types of medical procedures where stability with controlled movement is needed, such as in the treatment of scoliosis, there is a need for a non-cumbersome device that supports adjacent bone structures in relation to each other while allowing a predetermined amount of relative movement.
Another problem in fusion procedures is the invasion of the desired fusion space by fibrous ingrowths which block the fusion path.
It is desired, therefore, to provide system for applying compressive forces to bone structures to promote healing or fusion, to protect a fusion space from inadvertent invasion by non-fusion structures, and to address additional shortcomings inherent therein.
It is an object of the present invention to provide an orthopedic tensioning device for supporting adjacent bone structures relative to each other.
It is a further object of the present invention to provide an orthopedic cable system designed for efficient and safe installation and secure and precise maintenance of bone or implant bodies in precise positions and with selectively desired force. It is a further object of the present invention to provide means for protecting a fusion space from inadvertent blockage, while still enabling penetration by fusion material. These and other objects of the invention that are inherent and advantageous are disclosed herein.
In a preferred embodiment, the present invention cable system and method of installation are directed to a synthetic anterior intervertebral ligament (xe2x80x9cS.A.I.L.xe2x80x9d). The S.A.I.L. system is utilized for joining adjacent vertebral bodies between which one or more intervertebral fusion implants have been inserted via an anterior approach. The system comprises a cable, preferably of an ultra-high molecular weight polyethylene fiber, that is tied or otherwise fastened between two intervertebral bodies having one or more fusion devices implanted therebetween. The cable is tied in such a manner as to span the gap between the intervertebral bodies in which the one or more fusion devices reside. The technique of tying the cable and the optional use of additional tensioner devices are employed to achieve desired tension. Because of the nature of the vertebral bodies"" geometry on the anterior side, the present invention system and method contemplate forming one or more holes on each of the vertebral bodies to serve as loop holes through which the cable can pass to secure each vertebral body.
A patch or tube of mesh or other type of fabric, as will be described below, may be positioned and tensioned across the gap in order to add evenly distributed tension and to prevent the one or more fusion devices from migrating, particularly in a direction perpendicular to the vertebral column. The patch or tube also prevents inadvertent invasion of a fusion space by non-fusion bodies or structures, while enabling fusion growth therein. The patch or tube also provides means for holding bone graft material or bone morphogenic protein to facilitate and direct fusion growth. Selective positioning of bone graft material could be utilized to encourage the development of a sentinel sign fusion.
Another aspect of the present invention relates to utilization of a single strand of cable and/or a patch or tube that span a plurality of bone structures, such as vertebrae, in order to allow a controlled tension to be applied while allowing predetermined relative movement. Such a system can be implemented in, for example, the treatment of scoliosis. The patch or tube in that instance may be one or a plurality used in series.